Autoimmune Pulmonary Alveolar Proteinosis Complicated by Myelodysplastic Syndrome

Pulmonary alveolar proteinosis (PAP) is characterized by an abnormal surfactant accumulation in peripheral air spaces. Autoimmune PAP (APAP) results from macrophage dysfunction caused by anti-granulocytemacrophage colony-stimulating factor (GM-CSF) autoantibodies, and the presence of antibodies more than the cutoff value is specific for APAP. In contrast, secondary PAP (SPAP) does not require anti-GM-CSF autoantibodies and is complicated by other diseases, including myelodysplastic syndrome (MDS). A 73-yearold man with anemia and thrombocytopenia was diagnosed with APAP and MDS simultaneously. The measurement of serum anti-GM-CSF autoantibodies is important for the correct diagnosis and management of PAP, even with an established diagnosis of underlying SPAP-suggestive disease.